This invention relates to an apparatus for controlling the operating mode of a hydrocarbon distributor of electronic computer design.
More precisely the object of the invention is such a control apparatus utilizable notably in a hydrocarbon distributor in which there is a volumetric transducer allowing the measurement of the distributed hydrocarbon volume and including a mechanical output whose displacement is representative of the measured volume and a converter for associating with the displacement of the output device a number of pulses representative of the distributed volume. The distributor further comprises a set of electronic circuits making it possible to compute, from the pulses representing the measured volume and on the basis of unit price information, the cost corresponding to the distributed volume.
It will be understood that in such a type of distributor there is the coexistence of, on the one hand, elements in which the hydrocarbon flows and, on the other, electric or electronic circuits capable, during their operation, of causing short-circuits or sparks. It is thus necessary to separate the zone in which the electronic circuits are located from the zone in which the hydrocarbon flow lines are located, for obvious safety reasons.
A first solution of this problem consists in designing, from the outset, a distributor in which there is a first zone housing the components in which the hydrocarbon flows and a second zone in which all the electronic circuits are located, these two zones being separated by a hydrocarbon-vapor-proof partition forming an integral part of the distributor frame.
However, there are presently still a very large number of hydrocarbon distributors in which the calculation of the cost and its display are obtained by means of entirely mechanical devices. It is understood that, in this case, there is no risk of explosion. The distributor frame consequently does not include any particular sealing structure. Owing to the advantages offered by electronic computers (reliability, utilization flexibility, etc.), a large number of hydrocarbon distributor owners wish to replace their mechanical calculating device by an electronic computer. However, owing to the initial structure of the distributor frame, it would be very costly to install a hydrocarbon-proof partition to separate the components in which the hydrocarbon flows from the computer part.
The solution generally adopted consists in enclosing within an explosion-proof casing all the electronic circuits. The mechanical output of the volumetric transducer penetrates into the explosion-proof casing via a specially designed bushing. It is, however, necessary to be able to introduce into the computing circuits a certain amount of data to control the operating mode of the hydrocarbon distributor. These data consist mainly of the unit price of the hydrocarbon used for calculating the cost of the hydrocarbon delivered on the basis of the pumped volume. These data must be easily modified. Other data related to the operating mode should also be introducible. For example, it should be possible to control the distributor in the independent operating or self-service mode (remote-metering). It should also be possible to deliver to the computer many other types of data related to the operating mode, notably to control the display of the total volume distributed during a given period or the total amount of the sums invoiced to users during this same period.
The main problem lies in the fact that the information should be transmitted to the computing circuit through the explosion-proof casing without altering the properties of the latter. A first solution proposed consists in using push buttons which go through the explosion-proof casing, while complying with the established rules maintaining its explosion-proof characteristics. This makes it necessary, at each push button, to provide special explosion-proof arrangements and the structure of the casing is much more complex and its construction consequently much costlier. Another solution proposed consists in using a single mechanical device which goes through the explosion-proof casing. Relatively complex combinations of the movements of this mechanical device must be implemented to allow the introduction of all the required information. It is easily understood that such a single device involves a complex mechanical design and that, moreover, operating errors are liable to occur frequently. Furthermore, the total number of different types of data it is possible to introduce by means of such a system is necessarily limited.